1 files changed, 720 insertions, 0 deletions

diff --git a/pfinet/linux-src/net/ipv6/ip6_output.c b/pfinet/linux-src/net/ipv6/ip6_output.c
new file mode 100644
index 00000000..f67e3e9e
--- /dev/null
+++ b/pfinet/linux-src/net/ipv6/ip6_output.c
@@ -0,0 +1,720 @@
+/*
+ *	IPv6 output functions
+ *	Linux INET6 implementation 
+ *
+ *	Authors:
+ *	Pedro Roque		<roque@di.fc.ul.pt>	
+ *
+ *	$Id: ip6_output.c,v 1.1 2007/10/08 21:12:30 stesie Exp $
+ *
+ *	Based on linux/net/ipv4/ip_output.c
+ *
+ *	This program is free software; you can redistribute it and/or
+ *      modify it under the terms of the GNU General Public License
+ *      as published by the Free Software Foundation; either version
+ *      2 of the License, or (at your option) any later version.
+ *
+ *	Changes:
+ *	A.N.Kuznetsov	:	airthmetics in fragmentation.
+ *				extension headers are implemented.
+ *				route changes now work.
+ *				ip6_forward does not confuse sniffers.
+ *				etc.
+ *				
+ */
+
+#include <linux/errno.h>
+#include <linux/types.h>
+#include <linux/socket.h>
+#include <linux/net.h>
+#include <linux/netdevice.h>
+#include <linux/if_arp.h>
+#include <linux/in6.h>
+#include <linux/route.h>
+
+#include <net/sock.h>
+#include <net/snmp.h>
+
+#include <net/ipv6.h>
+#include <net/ndisc.h>
+#include <net/protocol.h>
+#include <net/ip6_route.h>
+#include <net/addrconf.h>
+#include <net/rawv6.h>
+#include <net/icmp.h>
+
+static u32	ipv6_fragmentation_id = 1;
+
+int ip6_output(struct sk_buff *skb)
+{
+	struct dst_entry *dst = skb->dst;
+	struct device *dev = dst->dev;
+	struct hh_cache *hh = dst->hh;
+
+	skb->protocol = __constant_htons(ETH_P_IPV6);
+	skb->dev = dev;
+
+	if (ipv6_addr_is_multicast(&skb->nh.ipv6h->daddr)) {
+		if (!(dev->flags&IFF_LOOPBACK) &&
+		    (skb->sk == NULL || skb->sk->net_pinfo.af_inet6.mc_loop) &&
+		    ipv6_chk_mcast_addr(dev, &skb->nh.ipv6h->daddr)) {
+			/* Do not check for IFF_ALLMULTI; multicast routing
+			   is not supported in any case.
+			 */
+			dev_loopback_xmit(skb);
+
+			if (skb->nh.ipv6h->hop_limit == 0) {
+				kfree_skb(skb);
+				return 0;
+			}
+		}
+
+		ipv6_statistics.Ip6OutMcastPkts++;
+	}
+
+	if (hh) {
+#ifdef __alpha__
+		/* Alpha has disguisting memcpy. Help it. */
+	        u64 *aligned_hdr = (u64*)(skb->data - 16);
+		u64 *aligned_hdr0 = hh->hh_data;
+		read_lock_irq(&hh->hh_lock);
+		aligned_hdr[0] = aligned_hdr0[0];
+		aligned_hdr[1] = aligned_hdr0[1];
+#else
+		read_lock_irq(&hh->hh_lock);
+		memcpy(skb->data - 16, hh->hh_data, 16);
+#endif
+		read_unlock_irq(&hh->hh_lock);
+	        skb_push(skb, dev->hard_header_len);
+		return hh->hh_output(skb);
+	} else if (dst->neighbour)
+		return dst->neighbour->output(skb);
+
+	kfree_skb(skb);
+	return -EINVAL;
+}
+
+/*
+ *	xmit an sk_buff (used by TCP)
+ */
+
+int ip6_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl,
+	     struct ipv6_txoptions *opt)
+{
+	struct ipv6_pinfo * np = sk ? &sk->net_pinfo.af_inet6 : NULL;
+	struct in6_addr *first_hop = fl->nl_u.ip6_u.daddr;
+	struct dst_entry *dst = skb->dst;
+	struct ipv6hdr *hdr;
+	u8  proto = fl->proto;
+	int seg_len = skb->len;
+	int hlimit;
+
+	if (opt) {
+		int head_room;
+
+		/* First: exthdrs may take lots of space (~8K for now)
+		   MAX_HEADER is not enough.
+		 */
+		head_room = opt->opt_nflen + opt->opt_flen;
+		seg_len += head_room;
+		head_room += sizeof(struct ipv6hdr) + ((dst->dev->hard_header_len + 15)&~15);
+
+		if (skb_headroom(skb) < head_room) {
+			struct sk_buff *skb2 = skb_realloc_headroom(skb, head_room);
+			kfree(skb);
+			skb = skb2;
+			if (skb == NULL)
+				return -ENOBUFS;
+			if (sk)
+				skb_set_owner_w(skb, sk);
+		}
+		if (opt->opt_flen)
+			ipv6_push_frag_opts(skb, opt, &proto);
+		if (opt->opt_nflen)
+			ipv6_push_nfrag_opts(skb, opt, &proto, &first_hop);
+	}
+
+	hdr = skb->nh.ipv6h = (struct ipv6hdr*)skb_push(skb, sizeof(struct ipv6hdr));
+
+	/*
+	 *	Fill in the IPv6 header
+	 */
+
+	*(u32*)hdr = __constant_htonl(0x60000000) | fl->fl6_flowlabel;
+	hlimit = -1;
+	if (np)
+		hlimit = np->hop_limit;
+	if (hlimit < 0)
+		hlimit = ((struct rt6_info*)dst)->rt6i_hoplimit;
+
+	hdr->payload_len = htons(seg_len);
+	hdr->nexthdr = proto;
+	hdr->hop_limit = hlimit;
+
+	ipv6_addr_copy(&hdr->saddr, fl->nl_u.ip6_u.saddr);
+	ipv6_addr_copy(&hdr->daddr, first_hop);
+
+	if (skb->len <= dst->pmtu) {
+		ipv6_statistics.Ip6OutRequests++;
+		dst->output(skb);
+		return 0;
+	}
+
+	printk(KERN_DEBUG "IPv6: sending pkt_too_big to self\n");
+	start_bh_atomic();
+	icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, dst->pmtu, skb->dev);
+	end_bh_atomic();
+	kfree_skb(skb);
+	return -EMSGSIZE;
+}
+
+/*
+ *	To avoid extra problems ND packets are send through this
+ *	routine. It's code duplication but I really want to avoid
+ *	extra checks since ipv6_build_header is used by TCP (which
+ *	is for us performace critical)
+ */
+
+int ip6_nd_hdr(struct sock *sk, struct sk_buff *skb, struct device *dev,
+	       struct in6_addr *saddr, struct in6_addr *daddr,
+	       int proto, int len)
+{
+	struct ipv6_pinfo *np = &sk->net_pinfo.af_inet6;
+	struct ipv6hdr *hdr;
+	int totlen;
+
+	skb->protocol = __constant_htons(ETH_P_IPV6);
+	skb->dev = dev;
+
+	totlen = len + sizeof(struct ipv6hdr);
+
+	hdr = (struct ipv6hdr *) skb_put(skb, sizeof(struct ipv6hdr));
+	skb->nh.ipv6h = hdr;
+
+	*(u32*)hdr = htonl(0x60000000);
+
+	hdr->payload_len = htons(len);
+	hdr->nexthdr = proto;
+	hdr->hop_limit = np->hop_limit;
+
+	ipv6_addr_copy(&hdr->saddr, saddr);
+	ipv6_addr_copy(&hdr->daddr, daddr);
+
+	return 0;
+}
+
+static struct ipv6hdr * ip6_bld_1(struct sock *sk, struct sk_buff *skb, struct flowi *fl,
+				  int hlimit, unsigned pktlength)
+{
+	struct ipv6hdr *hdr;
+	
+	skb->nh.raw = skb_put(skb, sizeof(struct ipv6hdr));
+	hdr = skb->nh.ipv6h;
+	
+	*(u32*)hdr = fl->fl6_flowlabel | htonl(0x60000000);
+
+	hdr->payload_len = htons(pktlength - sizeof(struct ipv6hdr));
+	hdr->hop_limit = hlimit;
+	hdr->nexthdr = fl->proto;
+
+	ipv6_addr_copy(&hdr->saddr, fl->nl_u.ip6_u.saddr);
+	ipv6_addr_copy(&hdr->daddr, fl->nl_u.ip6_u.daddr);
+	return hdr;
+}
+
+static __inline__ u8 * ipv6_build_fraghdr(struct sk_buff *skb, u8* prev_hdr, unsigned offset)
+{
+	struct frag_hdr *fhdr;
+
+	fhdr = (struct frag_hdr *) skb_put(skb, sizeof(struct frag_hdr));
+
+	fhdr->nexthdr  = *prev_hdr;
+	*prev_hdr = NEXTHDR_FRAGMENT;
+	prev_hdr = &fhdr->nexthdr;
+
+	fhdr->reserved = 0;
+	fhdr->frag_off = htons(offset);
+	fhdr->identification = ipv6_fragmentation_id++;
+	return &fhdr->nexthdr;
+}
+
+static int ip6_frag_xmit(struct sock *sk, inet_getfrag_t getfrag,
+			 const void *data, struct dst_entry *dst,
+			 struct flowi *fl, struct ipv6_txoptions *opt,
+			 struct in6_addr *final_dst,
+			 int hlimit, int flags, unsigned length, int mtu)
+{
+	struct ipv6hdr *hdr;
+	struct sk_buff *last_skb;
+	u8 *prev_hdr;
+	int unfrag_len;
+	int frag_len;
+	int last_len;
+	int nfrags;
+	int fhdr_dist;
+	int frag_off;
+	int data_off;
+	int err;
+
+	/*
+	 *	Fragmentation
+	 *
+	 *	Extension header order:
+	 *	Hop-by-hop -> Dest0 -> Routing -> Fragment -> Auth -> Dest1 -> rest (...)
+	 *	
+	 *	We must build the non-fragmented part that
+	 *	will be in every packet... this also means
+	 *	that other extension headers (Dest, Auth, etc)
+	 *	must be considered in the data to be fragmented
+	 */
+
+	unfrag_len = sizeof(struct ipv6hdr) + sizeof(struct frag_hdr);
+	last_len = length;
+
+	if (opt) {
+		unfrag_len += opt->opt_nflen;
+		last_len += opt->opt_flen;
+	}
+
+	/*
+	 *	Length of fragmented part on every packet but 
+	 *	the last must be an:
+	 *	"integer multiple of 8 octects".
+	 */
+
+	frag_len = (mtu - unfrag_len) & ~0x7;
+
+	/* Unfragmentable part exceeds mtu. */
+	if (frag_len <= 0) {
+		ipv6_local_error(sk, EMSGSIZE, fl, mtu);
+		return -EMSGSIZE;
+	}
+
+	nfrags = last_len / frag_len;
+
+	/*
+	 *	We must send from end to start because of 
+	 *	UDP/ICMP checksums. We do a funny trick:
+	 *	fill the last skb first with the fixed
+	 *	header (and its data) and then use it
+	 *	to create the following segments and send it
+	 *	in the end. If the peer is checking the M_flag
+	 *	to trigger the reassembly code then this 
+	 *	might be a good idea.
+	 */
+
+	frag_off = nfrags * frag_len;
+	last_len -= frag_off;
+
+	if (last_len == 0) {
+		last_len = frag_len;
+		frag_off -= frag_len;
+		nfrags--;
+	}
+	data_off = frag_off;
+
+	/* And it is implementation problem: for now we assume, that
+	   all the exthdrs will fit to the first fragment.
+	 */
+	if (opt) {
+		if (frag_len < opt->opt_flen) {
+			ipv6_local_error(sk, EMSGSIZE, fl, mtu);
+			return -EMSGSIZE;
+		}
+		data_off = frag_off - opt->opt_flen;
+	}
+
+	last_skb = sock_alloc_send_skb(sk, unfrag_len + frag_len +
+				       dst->dev->hard_header_len + 15,
+				       0, flags & MSG_DONTWAIT, &err);
+
+	if (last_skb == NULL)
+		return err;
+
+	last_skb->dst = dst_clone(dst);
+
+	skb_reserve(last_skb, (dst->dev->hard_header_len + 15) & ~15);
+
+	hdr = ip6_bld_1(sk, last_skb, fl, hlimit, frag_len+unfrag_len);
+	prev_hdr = &hdr->nexthdr;
+
+	if (opt && opt->opt_nflen)
+		prev_hdr = ipv6_build_nfrag_opts(last_skb, prev_hdr, opt, final_dst, 0);
+
+	prev_hdr = ipv6_build_fraghdr(last_skb, prev_hdr, frag_off);
+	fhdr_dist = prev_hdr - last_skb->data;
+
+	err = getfrag(data, &hdr->saddr, last_skb->tail, data_off, last_len);
+
+	if (!err) {
+		while (nfrags--) {
+			struct sk_buff *skb;
+			
+			struct frag_hdr *fhdr2;
+				
+			skb = skb_copy(last_skb, sk->allocation);
+
+			if (skb == NULL) {
+				ipv6_statistics.Ip6FragFails++;
+				kfree_skb(last_skb);
+				return -ENOMEM;
+			}
+			
+			frag_off -= frag_len;
+			data_off -= frag_len;
+
+			fhdr2 = (struct frag_hdr *) (skb->data + fhdr_dist);
+
+			/* more flag on */
+			fhdr2->frag_off = htons(frag_off | 1);
+
+			/* Write fragmentable exthdrs to the first chunk */
+			if (nfrags == 0 && opt && opt->opt_flen) {
+				ipv6_build_frag_opts(skb, &fhdr2->nexthdr, opt);
+				frag_len -= opt->opt_flen;
+				data_off = 0;
+			}
+
+			err = getfrag(data, &hdr->saddr,skb_put(skb, frag_len),
+				      data_off, frag_len);
+
+			if (err) {
+				kfree_skb(skb);
+				break;
+			}
+
+			ipv6_statistics.Ip6FragCreates++;
+			ipv6_statistics.Ip6OutRequests++;
+			dst->output(skb);
+		}
+	}
+
+	if (err) {
+		ipv6_statistics.Ip6FragFails++;
+		kfree_skb(last_skb);
+		return -EFAULT;
+	}
+
+	hdr->payload_len = htons(unfrag_len + last_len - sizeof(struct ipv6hdr));
+
+	/*
+	 *	update last_skb to reflect the getfrag we did
+	 *	on start.
+	 */
+
+	skb_put(last_skb, last_len);
+
+	ipv6_statistics.Ip6FragCreates++;
+	ipv6_statistics.Ip6FragOKs++;
+	ipv6_statistics.Ip6OutRequests++;
+	dst->output(last_skb);
+
+	return 0;
+}
+
+int ip6_build_xmit(struct sock *sk, inet_getfrag_t getfrag, const void *data,
+		   struct flowi *fl, unsigned length,
+		   struct ipv6_txoptions *opt, int hlimit, int flags)
+{
+	struct ipv6_pinfo *np = &sk->net_pinfo.af_inet6;
+	struct in6_addr *final_dst = NULL;
+	struct dst_entry *dst;
+	int err = 0;
+	unsigned int pktlength, jumbolen, mtu;
+	struct in6_addr saddr;
+
+	if (opt && opt->srcrt) {
+		struct rt0_hdr *rt0 = (struct rt0_hdr *) opt->srcrt;
+		final_dst = fl->fl6_dst;
+		fl->fl6_dst = rt0->addr;
+	}
+
+	if (!fl->oif && ipv6_addr_is_multicast(fl->nl_u.ip6_u.daddr))
+		fl->oif = np->mcast_oif;
+
+	dst = NULL;
+	if (sk->dst_cache) {
+		dst = dst_check(&sk->dst_cache, np->dst_cookie);
+		if (dst) {
+			struct rt6_info *rt = (struct rt6_info*)dst_clone(dst);
+
+			/* Yes, checking route validity in not connected
+			   case is not very simple. Take into account,
+			   that we do not support routing by source, TOS,
+			   and MSG_DONTROUTE 		--ANK (980726)
+
+			   1. If route was host route, check that
+			      cached destination is current.
+			      If it is network route, we still may
+			      check its validity using saved pointer
+			      to the last used address: daddr_cache.
+			      We do not want to save whole address now,
+			      (because main consumer of this service
+			       is tcp, which has not this problem),
+			      so that the last trick works only on connected
+			      sockets.
+			   2. oif also should be the same.
+			 */
+			if (((rt->rt6i_dst.plen != 128 ||
+			      ipv6_addr_cmp(fl->fl6_dst, &rt->rt6i_dst.addr))
+			     && (np->daddr_cache == NULL ||
+				 ipv6_addr_cmp(fl->fl6_dst, np->daddr_cache)))
+			    || (fl->oif && fl->oif != dst->dev->ifindex)) {
+				dst_release(dst);
+				dst = NULL;
+			}
+		}
+	}
+
+	if (dst == NULL)
+		dst = ip6_route_output(sk, fl);
+
+	if (dst->error) {
+		ipv6_statistics.Ip6OutNoRoutes++;
+		dst_release(dst);
+		return -ENETUNREACH;
+	}
+
+	if (fl->fl6_src == NULL) {
+		err = ipv6_get_saddr(dst, fl->fl6_dst, &saddr);
+
+		if (err) {
+#if IP6_DEBUG >= 2
+			printk(KERN_DEBUG "ip6_build_xmit: "
+			       "no availiable source address\n");
+#endif
+			goto out;
+		}
+		fl->fl6_src = &saddr;
+	}
+	pktlength = length;
+
+	if (hlimit < 0) {
+		if (ipv6_addr_is_multicast(fl->fl6_dst))
+			hlimit = np->mcast_hops;
+		else
+			hlimit = np->hop_limit;
+		if (hlimit < 0)
+			hlimit = ((struct rt6_info*)dst)->rt6i_hoplimit;
+	}
+
+	jumbolen = 0;
+
+	if (!sk->ip_hdrincl) {
+		pktlength += sizeof(struct ipv6hdr);
+		if (opt)
+			pktlength += opt->opt_flen + opt->opt_nflen;
+
+		if (pktlength > 0xFFFF + sizeof(struct ipv6hdr)) {
+			/* Jumbo datagram.
+			   It is assumed, that in the case of sk->ip_hdrincl
+			   jumbo option is supplied by user.
+			 */
+			pktlength += 8;
+			jumbolen = pktlength - sizeof(struct ipv6hdr);
+		}
+	}
+
+	mtu = dst->pmtu;
+	if (np->frag_size < mtu) {
+		if (np->frag_size)
+			mtu = np->frag_size;
+		else if (np->pmtudisc == IPV6_PMTUDISC_DONT)
+			mtu = IPV6_MIN_MTU;
+	}
+
+	/* Critical arithmetic overflow check.
+	   FIXME: may gcc optimize it out? --ANK (980726)
+	 */
+	if (pktlength < length) {
+		ipv6_local_error(sk, EMSGSIZE, fl, mtu);
+		err = -EMSGSIZE;
+		goto out;
+	}
+
+	if (pktlength <= mtu) {
+		struct sk_buff *skb;
+		struct ipv6hdr *hdr;
+		struct device *dev = dst->dev;
+
+		skb = sock_alloc_send_skb(sk, pktlength + 15 +
+					  dev->hard_header_len, 0,
+					  flags & MSG_DONTWAIT, &err);
+
+		if (skb == NULL) {
+			ipv6_statistics.Ip6OutDiscards++;
+			goto out;
+		}
+
+		skb->dst = dst_clone(dst);
+
+		skb_reserve(skb, (dev->hard_header_len + 15) & ~15);
+
+		hdr = (struct ipv6hdr *) skb->tail;
+		skb->nh.ipv6h = hdr;
+
+		if (!sk->ip_hdrincl) {
+			ip6_bld_1(sk, skb, fl, hlimit,
+				  jumbolen ? sizeof(struct ipv6hdr) : pktlength);
+
+			if (opt || jumbolen) {
+				u8 *prev_hdr = &hdr->nexthdr;
+				prev_hdr = ipv6_build_nfrag_opts(skb, prev_hdr, opt, final_dst, jumbolen);
+				if (opt && opt->opt_flen)
+					ipv6_build_frag_opts(skb, prev_hdr, opt);
+			}
+		}
+
+		skb_put(skb, length);
+		err = getfrag(data, &hdr->saddr,
+			      ((char *) hdr) + (pktlength - length),
+			      0, length);
+
+		if (!err) {
+			ipv6_statistics.Ip6OutRequests++;
+			dst->output(skb);
+		} else {
+			err = -EFAULT;
+			kfree_skb(skb);
+		}
+	} else {
+		if (sk->ip_hdrincl || jumbolen ||
+		    np->pmtudisc == IPV6_PMTUDISC_DO) {
+			ipv6_local_error(sk, EMSGSIZE, fl, mtu);
+			err = -EMSGSIZE;
+			goto out;
+		}
+
+		err = ip6_frag_xmit(sk, getfrag, data, dst, fl, opt, final_dst, hlimit,
+				    flags, length, mtu);
+	}
+
+	/*
+	 *	cleanup
+	 */
+out:
+	ip6_dst_store(sk, dst, fl->nl_u.ip6_u.daddr == &np->daddr ? &np->daddr : NULL);
+	return err;
+}
+
+int ip6_call_ra_chain(struct sk_buff *skb, int sel)
+{
+	struct ip6_ra_chain *ra;
+	struct sock *last = NULL;
+
+	for (ra = ip6_ra_chain; ra; ra = ra->next) {
+		struct sock *sk = ra->sk;
+		if (sk && ra->sel == sel) {
+			if (last) {
+				struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
+				if (skb2)
+					rawv6_rcv(last, skb2, skb2->len);
+			}
+			last = sk;
+		}
+	}
+
+	if (last) {
+		rawv6_rcv(last, skb, skb->len);
+		return 1;
+	}
+	return 0;
+}
+
+int ip6_forward(struct sk_buff *skb)
+{
+	struct dst_entry *dst = skb->dst;
+	struct ipv6hdr *hdr = skb->nh.ipv6h;
+	struct inet6_skb_parm *opt =(struct inet6_skb_parm*)skb->cb;
+	
+	if (ipv6_devconf.forwarding == 0 && opt->srcrt == 0)
+		goto drop;
+
+	/*
+	 *	We DO NOT make any processing on
+	 *	RA packets, pushing them to user level AS IS
+	 *	without ane WARRANTY that application will be able
+	 *	to interpret them. The reason is that we
+	 *	cannot make anything clever here.
+	 *
+	 *	We are not end-node, so that if packet contains
+	 *	AH/ESP, we cannot make anything.
+	 *	Defragmentation also would be mistake, RA packets
+	 *	cannot be fragmented, because there is no warranty
+	 *	that different fragments will go along one path. --ANK
+	 */
+	if (opt->ra) {
+		u8 *ptr = skb->nh.raw + opt->ra;
+		if (ip6_call_ra_chain(skb, (ptr[2]<<8) + ptr[3]))
+			return 0;
+	}
+
+	/*
+	 *	check and decrement ttl
+	 */
+	if (hdr->hop_limit <= 1) {
+		/* Force OUTPUT device used as source address */
+		skb->dev = dst->dev;
+		icmpv6_send(skb, ICMPV6_TIME_EXCEED, ICMPV6_EXC_HOPLIMIT,
+			    0, skb->dev);
+
+		kfree_skb(skb);
+		return -ETIMEDOUT;
+	}
+
+	/* IPv6 specs say nothing about it, but it is clear that we cannot
+	   send redirects to source routed frames.
+	 */
+	if (skb->dev == dst->dev && dst->neighbour && opt->srcrt == 0) {
+		struct in6_addr *target = NULL;
+		struct rt6_info *rt;
+		struct neighbour *n = dst->neighbour;
+
+		/*
+		 *	incoming and outgoing devices are the same
+		 *	send a redirect.
+		 */
+
+		rt = (struct rt6_info *) dst;
+		if ((rt->rt6i_flags & RTF_GATEWAY))
+			target = (struct in6_addr*)&n->primary_key;
+		else
+			target = &hdr->daddr;
+
+		/* Limit redirects both by destination (here)
+		   and by source (inside ndisc_send_redirect)
+		 */
+		if (xrlim_allow(dst, 1*HZ))
+			ndisc_send_redirect(skb, n, target);
+	} else if (ipv6_addr_type(&hdr->saddr)&(IPV6_ADDR_MULTICAST|IPV6_ADDR_LOOPBACK
+						|IPV6_ADDR_LINKLOCAL)) {
+		/* This check is security critical. */
+		goto drop;
+	}
+
+	if (skb->len > dst->pmtu) {
+		/* Again, force OUTPUT device used as source address */
+		skb->dev = dst->dev;
+		icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, dst->pmtu, skb->dev);
+		ipv6_statistics.Ip6InTooBigErrors++;
+		kfree_skb(skb);
+		return -EMSGSIZE;
+	}
+
+	if ((skb = skb_cow(skb, dst->dev->hard_header_len)) == NULL)
+		return 0;
+
+	hdr = skb->nh.ipv6h;
+
+	/* Mangling hops number delayed to point after skb COW */
+ 
+	hdr->hop_limit--;
+
+	ipv6_statistics.Ip6OutForwDatagrams++;
+	return dst->output(skb);
+
+drop:
+	ipv6_statistics.Ip6InAddrErrors++;
+	kfree_skb(skb);
+	return -EINVAL;
+}